De Niro's first film role in collaboration with Brian De Palma materialized in 1963 at the age of 20, when he appeared in The Wedding Party; however, the film was not released until 1969. He spent much of the 1960s working in theater workshops and off-Broadway productions. He was an extra in the French film Three Rooms in Manhattan (1965) and made his official film debut after he reunited with De Palma in Greetings (1968). He later reprised his Greetings role in Hi, Mom (1970).

De Niro on the set of Raging Bull with Jake LaMotta .He gained popular attention with his role as a dying Major League baseball player in Bang the Drum Slowly (1973). The same year, he began his fruitful collaboration with Scorsese when he played a memorable role as the smalltime hood "Johnny Boy" alongside Harvey Keitel's "Charlie" in Mean Streets (1973). In 1974, De Niro played a pivotal role in Francis Coppola's The Godfather, Part II, playing young Don Vito Corleone, having previously auditioned for the roles of Sonny Corleone, Michael Corleone, Carlo Rizzi and Paulie Gatto in the first film. His performance earned him his first Academy Award, for Best Supporting Actor, although Coppola accepted the award, as De Niro was not present at the Oscar ceremony. He became the first actor to win an Academy Award speaking mainly a foreign language, in this case, multiple Sicilian dialects (although he delivered a few lines in English). De Niro and Marlon Brando, who played the older Vito Corleone in the first film, are the only actors to have won leading-role Oscars portraying the same fictional character.

After working with Scorsese in Mean Streets, he had a very successful working relationship with the director in films such as Taxi Driver (1976), New York, New York (1977), Raging Bull (1980), The King of Comedy (1983), Goodfellas (1990), Cape Fear (1991), and Casino (1995). They also acted together in Guilty by Suspicion and provided their voices for the animated feature Shark Tale.

In many of his films, De Niro has played charming sociopaths. Taxi Driver is particularly important to De Niro's career; his iconic performance as Travis Bickle shot him to stardom and forever linked De Niro's name with Bickle's famous "You talkin' to me?" monologue, which De Niro improvised. In 1976, De Niro appeared (along with Gérard Depardieu and Donald Sutherland) in Bernardo Bertolucci's epic biographical exploration of life during World War II, Novecento (1900), seen through the eyes of two Italian childhood friends at the opposite sides of society's hierarchy.

In 1978, De Niro played "Michael Vronsky" in the acclaimed Vietnam War film The Deer Hunter, for which he was nominated Best Actor in a Leading Role.

Praised for his commitment to roles (stemming from his background in Method acting), De Niro gained 60 pounds (27 kg) and learned how to box for his portrayal of Jake LaMotta in Raging Bull; ground his teeth for Cape Fear; lived in Sicily for The Godfather, Part II; worked as a cab driver for three months for Taxi Driver; and learned to play the saxophone for New York, New York. He also put on weight and shaved his hairline to play Al Capone in The Untouchables.

De Niro's brand of method acting includes employing whatever extreme tactic he feels is necessary to elicit the best performance from those he is acting with. During the filming of The King of Comedy, for example, he directed a slew of anti-Semitic epithets at costar Jerry Lewis in order to enhance and authenticate the anger demonstrated by his onscreen character. According to People magazine, the technique was successful. Lewis recalled, "I forgot the cameras were there... I was going for Bobby's throat".

Fearing he had become typecast in mob roles, De Niro began expanding into occasional comedic roles in the mid-1980s and has had much success there as well, with such films as Brazil (1985) (in which he had a small role); the hit action-comedy Midnight Run (1988), Showtime (2002), opposite Eddie Murphy; the film-and-sequel pairs Analyze This (1999) & Analyze That (2002), both opposite actor/comedian Billy Crystal, Meet the Parents (2000) and Meet the Fockers (2004).

Other films include Falling in Love (1984), The Mission (1986), Angel Heart (1987), Awakenings (1990), opposite Robin Williams, where De Niro plays a catatonic patient brought to life by medication, Heat (1995), The Fan (1996), opposite Wesley Snipes, where De Niro plays an obsessive psychotic baseball fanatic, Wag the Dog (1997), and Ronin (1998). In 1997, he reteamed with Harvey Keitel and Ray Liotta along with Sylvester Stallone in the crime drama Cop Land. De Niro played a supporting role, taking a back seat to Stallone, Keitel, and Liotta.

In 1993 he also starred in This Boy's Life, featuring then-rising child actors Leonardo DiCaprio and Tobey Maguire. Around this time, he was offered the role of psychotic killer Mitch Leary in In the Line of Fire opposite Clint Eastwood, but he turned the role down in favor of John Malkovich.

In 1995, De Niro starred in Michael Mann's police action-thriller Heat, along with fellow actor, long-time rival and friend, Al Pacino. The duo drew much attention from fans, as both have generally been compared throughout their careers. Though both Pacino and De Niro starred in The Godfather, Part II, they shared no screen time. De Niro and Pacino once again appeared in a film together, as police investigators hunting a serial killer in the hardcore crime thriller Righteous Kill.

In 2004, De Niro provided the voice of Don Lino, the antagonist in the animated film Shark Tale, opposite Will Smith. He also reprised his role as Jack Byrnes in Meet the Fockers, and was featured in Stardust. All films were successful at the box office but received mixed reviews. When promoting Shark Tale, De Niro said that was his first experience with voice acting, which he commented was an enjoyable time.

De Niro had to turn down a role in The Departed (Martin Sheen taking the role instead) due to commitments with preparing The Good Shepherd. He said "I wanted to. I wish I could've been able to, but I was preparing The Good Shepherd so much that I couldn't take the time to. I was trying to figure a way to do it while I was preparing. It just didn't seem possible."

In June 2006, it was announced that De Niro had donated his film archive—including scripts, costumes, and props—to the Harry Ransom Center at The University of Texas at Austin. De Niro has said that he is working with Martin Scorsese on a new project. "I'm trying to actually work... [screenwriter] Eric Roth and myself and Marty are working on a script now, trying to get it done."

De Niro has won two Academy Awards: Best Actor for his role in Raging Bull, and Best Supporting Actor for The Godfather, Part II.

De Niro and Marlon Brando are the only actors who won Academy Awards for portraying the same character: Brando won for playing the elderly Don Vito Corleone (though he declined the award) in The Godfather, while De Niro later won the award for playing the young Vito in The Godfather, Part II. Brando and De Niro came together onscreen for the only time in The Score (2001). De Niro actually auditioned for the role of Sonny in the first Godfather,[12] but the role was given to James Caan. When The Godfather, Part II was in preproduction, the director, Francis Ford Coppola, remembered De Niro's audition and cast him to play the young Vito Corleone. De Niro is one of only five people to win an Academy Award for working in a foreign language, as he almost exclusively spoke Italian, with very few phrases in English.

De Niro is acting in the role of a mobster in Paramount Pictures' upcoming movie, Frankie Machine. He announced that he would appear in Martin Campbell's film version of the classic BBC crime series Edge of Darkness in 2009 alongside Mel Gibson, however, just after he arrived to begin shooting, De Niro walked from the set due to creative differences.[13] He was then replaced by Ray Winstone. (source wikipedia.org)